Process for pickling aluminium and its alloys prior to galvanizing or coating the same with other metals.



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WETED STATE% PATET FFIQE. STEPHAN J'AHN, OF CHABLOTTENBURG, GERMANY;ASSIG-NOR T AKTIENG-ESELL- SCHAFT MIX & GENEST,YTELEPHQN- UNDTELEGRAPQEN WERKE, 0F BERLIN, GER- MANY, A FIRM.

P ROGESS FOR PICKLING ALUMINIUM AND ITS ALLOYS PRIOR TO GALVANIZING 0R-COATING THE SAME WITH OTHER METALS.

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Specification of Letters Patent.

Application filed .Tune' 16, 1910. Serial No. 567,189.

Patented Dec. 112, 1911.

Alloys Prior to'Galvanizing or Coating the Same with other Metals, ofwhich the following is a specification.

This invention relates to the coatin of aluminium and its alloys with orwit out the use of electric current, and particularly to processes forpickling aluminlum and its alloys to prepare them for the coatingoperation.

Various attempts have been made in the past to solve the problem of thecoating of aluminium, but in all the processes previously proposeddefects or difficulties have been encountered which have prevented theseprocesses from being applied in practice to any considerable extent. Insome of the known processes the aluminium has been etched or corroded bymeans of alkalis, sometimes in a boiling bath and sometimes with the aidof an electric current. In other cases baths containing sulfuric aciddiluted with water and with a small addition of boracic acid or ofphosphate of sodium and sulfate of magnesium have been suggested, thetreatment in such a bath to be followed by a rinsing operation andimmersion in another bath of sulfuric acid with nitrate of soda andsmall additions of other substances including hydrochloric acid.

As distinguished from such processes, the

present invention relates to a process in Y which acids of the halogengroup are used diluted with water, and with the addition of furtherreagents intended to serve for restraining or checking the reaction. Inrocesses according to this invention the aths do not require to beraised to a boiling point, and a temperature of 70 C. is quitesufficient to enable the required reaction to take place. The weaker thebaths and the lower their temperatures, the slower will the pickling beeffected and the less risk will there be of the aluminium being toostrongly attacked, but the weakness of the baths is limited byconsiderations of the length of time which the pickling process can beallowed to occupy. Examples hereinafter given will indicateapproximately the best conditions of working.

In working according to the present invention the aluminium to be coatedwith other metals, is first cleaned and freed from grease in an knownmanner. After this it 15 inserted lnto a bath containing one or more ofthe acids of the halogen group diluted with water and containing also 1frequired suitable reagents for restricting or checking the reaction,such for example as ordinary (ethyl) alcohol or other alcohols such asgl cerin; organic acids containing hydroxyl OH) groups; and gelatin orlike substances which are soluble in the baths can also be used asrestraining or checking agents. As an instance of such a bath may bementioned a mixture of 500 s. of hydrochloric acid with 1000 grs. ofwater and I50 grs. of ethyl alcohol, kept at about 7 0 (1;

or if hydrofluoric acid is used the bath may contain 10 grs. of thisacid in 1000 grs. of water, with at least 15 grs. of ethyl alcohol.

Other examples of baths with others of the restricting agents abovementioned, are as follows :The bath may be at about 70 C., and besides1000 grs. of water it may contain (a) 500 grs. of hydrochloric acid with150 grs. of glycerin, or with 30 grs.

with 1000 grs. of water.

If the baths above mentioned as being used at about 70 (1., are used atlower temperatures such as 40 (1., they may be made rather stronger; andvice versa, the last bath above mentioned should be made still weaker ifits temperature is to be raised much above 40 C.

I claim:

1. Process for pickling aluminium and its alloys prior to coating thesame with other metals, in which the aluminium is first freed fromgrease and the like, and then immersed in a heated pickling bathcontainin diluted acid of the halogen group, with t e addition ofrestraining agents, substantially as described.

2. Process for pickling aluminiumand its alloys prior to coatin the samewith other metals, in which the a uminium is first freed from grease andthe like, and then immersed in a heated pickling bath containing dilutedacid of the halo en group, with the addition of an alcohol, sustantially as described.

3. Process for pickling aluminium and its alloys prior to coatin thesame with other metals, in which the a uminium is first freed fromgrease and the like, and then immersed in a heated pickling bathcontaining diluted acid of the halo en group, with the addition of ahigher a cohol, substantially as described.

4. Process for pickling aluminium and its alloys prior to coating thesame with other metals, in which the aluminium is first freed fromgrease and the like, and then immersed in a heated pickling bathcontaining diluted acid of the halogen group, with the addition ofglycerin, substantially as described.

In testimon whereof I affix my signature in presence 0 two witnesses.

STEPHAN JA'HN.

Witnesses:

WOLDEMAR HAUPT, ARTHUR SGHROEDER.

